Known tire building drums usually utilize a number of external bladders, which are inflated during manufacture of the tire for preforming the inner carcass and turning the lower sidewall portions of the tire about and over the beads, usually metal beads, secured to the drum by fastening devices on the drum itself.
Due to the mechanical strain they are subjected to and the special function they are called upon to perform, bladders of the aforementioned type are usually, but not necessarily, provided with strengthening or reinforcing plies, and are generally hand made and cured in an autoclave using a relatively time-consuming, high-cost manufacturing process.